1. Field of the Invention:
The present invention relates to the field of determining the optical density (opacity) of a fluid, and more particularly, the determination of light extinction in a fluid using laser light.
2. Art Background:
There has long been a need to measure the density of sprays, gas flows, planetary atmospheres, combustion processes and the like. Such measurements are useful in combustion and nozzle applications, fuel analysis, planetary studies, etc. A number of techniques employing laser light to determine the extinction of a gas flow, and thereby its optical density, have been developed. In one system, the fluid is passed through a tube or conduit having windows aligned across the fluid flow. A laser beam is directed through one window and into the fluid flow, exiting out of a second window. By examining the intensity of the exiting beam, and knowing the distance traversed, the optical fluid density may be determined by the extinction characteristics of the beam. One common problem which leads to inaccuracy in such prior art systems is particulate deposition on the window inside the conduit passing the fluid. The deposition of particulates on the interior surfaces of the windows alters the extinction characteristics of the laser light, thereby resulting in an artificially high optical fluid density determination.
As will be described, the present invention provides a unique fluid density probe for use in determining light extinction through a fluid independent of the transmission coefficient through the access windows.